1. Field of the Invention
The present invention relates generally to an internet protocol telephony system, and in particular, to an apparatus and method for compulsively (i.e., irregardless of whether or not the destination party responds) receiving multi-calls (or group calls) between IP terminals in internet protocol telephony system.
2. Description of the Related Art
According to recent rapid spread of and diverse service requirements to the internet, an IP(Internet Protocol)-based network or packet-based network (hereinafter totally called “IP network”) is being brilliantly developed in not only an aspect of performance but also an aspect of service. For example, although the IP network is typically realized in consideration of data transfer, it is also required to transfer voice. According to this kind of requirement, the IP network is extended to make multimedia services possible. That is, it is possible to transfer video and data as well as voice like the conventional communication network through the IP network. In an aspect that voice call between subscribers is possible by transferring voice, the IP network is called “VoIP” (Voice over IP) system or “Internet Protocol Telephony System”. As described above, the voice transfer with data through the IP network now plays a key role in the IP network. Under these circumstances, various research on transferring voice via the IP network are undertaken.
For example, H.323 standards, communication specifications on multimedia of ITU-T(International Telecommunication Union-Telecommunication) provide a frame for voice, video and data communication through the IP network including the internet. One of H.323 entities defined in the H.323 protocols is a gatekeeper. The gatekeeper is to bind H.323 endpoints existing in the IP network to a control domain defined as “zone” and to control, manage and incorporate them. For example, the H.323 endpoints include gateways, terminals and MCUs(Multi-point Control Units), etc. The zone is composed of one gatekeeper and one H.323 endpoint or more. Plural gatekeepers can compose multi-zones and another gatekeeper can exist to control the multi-zones.
There are major functions of gatekeeper such as address translation, call admission, bandwidth control, call control and maintenance, etc. The address translation function means to translate an virtual name or a destination number to a network address, namely an IP address. The call admission function means a function of RAS(Registration/Admission/Status), totally named for protocols relating to gatekeepers in H.323. The bandwidth control function means to allot bandwidth, which is a limited resource of network, to each endpoint, check if the allotted bandwidth reaches a limit value and block over-limit value. The call control function means to connect/cancel calls among endpoints via the gatekeeper as an intermediate device. The maintenance function means an additive function such as charge or statistics, etc.
The RAS is a basic signaling protocol of the gatekeeper. The RAS is a protocol of realizing a basic interface between a gatekeeper and endpoints such as phones, gateways and MCUs, etc. The gatekeeper corresponds to a server and the endpoints do to clients in the RAS. Namely, the RAS is an essential and fundamental protocol through which the gatekeeper as the server operates and controls endpoints as clients. The gatekeeper also checks status of the endpoints through the RAS to reflect the results on controlling them. In the RAS, the registration is that each endpoint as the client registers itself to the gatekeeper as the server. The admission is that the gatekeeper checks if the clients satisfy rules of the H.323 and corresponding zone to admit an access to the VoIP network. Here, the access to the VoIP network means initial setup of a VoIP call. The H.323 rules are to check if virtual names and registration IDs(Identifications) of each endpoint are overlapped with the ones of the other endpoints. The zone rules are to check if the corresponding endpoints are registered to the gatekeeper. The status is to report current situation and information on each endpoint to the gatekeeper periodically. Therefore, the gatekeeper can obtain information, which is necessary to operate and control the endpoints, and test links between the server and the clients periodically.
As described above, the IP-phones and the gatekeeper are interfaced according to the RAS, which is the H.323 protocol of ITU-T specifications. According to the conventional VoIP system or IP telephony system, there provides a multi-point controller (hereinafter called “MC”). However, there occurs inconvenience in operation of it as follows.
First, the MC function is to invite the next IP terminal, connect and perform the next call after one-to-one call. That is, the conventional MC function has purpose to realize multi-calls, not one-to-many calls. Accordingly, a function of making calls to plural destination IP terminals and talking to them at the same time cannot be provided through the MC function.
Second, a call becomes set up when a destination IP terminal responds to the call in the MC function. Therefore, a call cannot be made in case that a destination IP terminal does not respond. Accordingly, there is a problem that cannot accomplish the fundamental purpose of information share or rapid information transfer, if a call would be not set up when someone tries to make an urgent call.
Third, although an effective multi-calls can be realized by using the MC function, it is difficult to design message flow of them and manage them. It is also difficult to make one-to-many calls by a single call request.